Retry
In depth research of ultimate Pebble mine
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Knowledge is Power
To start off, it is instructive to see
what is happening with the
Bristol Bay Native Corporation
The Bristol Bay Native Corporation (BBNC) is the only one of the 13 Native Corporations that is against the Pebble mine. The elected leaders of the BBNC are virulent antagonists of the Pebble mine, but it is the Alaskan Natives of the area that are the true people in charge of the corporation, through their privately owned shares of corporation stock.
Last year Pebble Limited Partnership created an {advisory board} and asked people to join it, including Pebble opponents. So that Pebble could interact directly with them, listen to their concerns, and work with them in resolving them.
One of BBNC's board members announced that she was going to talk to the Pebble Partnership. She said that she was not for the Pebble mine at this time, but that it would only be fair to the people in her jurisdiction to find out what Pebble had in mind for the mine, and see if it would actually harm the Bristol Bay area.
BBNC's management were furious. They ostracized her. They got her neighbors to lecture her. They did this non-stop, and she finally resigned.
However, this made other members furious at the BBNC management. Two board members stepped forward and said that they were going to take her place, and talk to the Pebble Partnership, and that nobody was going to intimidate them into resigning.
In addition to that, Abe Williams, a BBNC shareholder, and fourth-generation Bristol Bay fisherman, wrote an {opinions piece:}
"Bristol Bay Native Corp. needs to rethink the region’s needs and its opposition to Pebble."
In it, he said what he found concerning, was "the recent censorship and bullying towards one of its own board members. They took this action not because someone changed their opposition to Pebble, but for accepting a seat on an advisory panel to have the option for meaningful engagement and understanding of the project by those who promote it."
"I have watched our leaders' performance for some time and wanted to raise my concerns in a forum where they could be heard, and I am not alone in expecting more from our leaders."
"We need to include open minded review of the Pebble Partnership's plan for a mine site near Iliamna, the infrastructure to support it, and possible benefits for the area."
"Over the recent years the BBNC leadership has deeply rooted itself into its opposition of the Pebble project, to the point they have taken a negative aim not only at shareholders who support more of an open-minded approach. Bristol Bay Native Corporation needs to rethink the region’s needs and its opposition to Pebble."
"The question I want to pose to our leaders is what do you fear from discussion and conversation? This is how we learn and how we stay informed. To do less than this, in my opinion, is a severe dereliction of stewardship and leadership."
"Perhaps it's time to review our corporation's election processes to ensure equal opportunity is afforded to all possible candidates. I personally think we should have greater regional representation on our board so that more perspectives make their way into the board room when decisions are being made. I also think we should consider the concept of reasonable term limits so that we attract a broader range of people to help our corporation."
Opposition is building within the BBNC to its stand against the Pebble mine
Many Native Alaskans say
YES to PEBBLE
Lisa Reimers, a board member of Iliamna Natives Limited, said that their position on the mine is neutral. Before they decide anything, they want Northern Dynasty to be allowed to go through the permitting process and then present their side of the story.
The Iliamna leaders wanted to talk to the Native Alaska villagers opposed to the project, and have an "open robust debate about what is at stake." But the villagers that were fighting the mine refused to talk to them.
For example, Robin Samuelsen, a chief with the Curyung Tribal Council, a director with the Bristol Bay Native Corporation, and the chairman of the Bristol Bay Economic Development Corporation’s board of directors, said, "Not having seen the plan, I will still oppose the mine."
The Pebble deposit sits within the Lake and Peninsula borough boundaries. Nathan Hill, the manager of the Lake and Peninsula Borough, said, "The position of the Borough is neutral. Because of that, we have been targeted by Pebble mine opponents, notably Alaska's wealthiest resident, Bob Gillam, who has funded several lawsuits against us." "The Borough has spent hundreds of thousands of dollars fighting frivolous lawsuits."
Bob Gillam is a self made billionaire who owns a hunting and fishing lodge in the area. He says that he has dedicated millions to stopping the Pebble project. That Pebble will leave behind a wasteland. His critics point out that he never provides any facts to back up his claims.
Newhalen, which is one of the two closest villages to the mine site, is for the Pebble mine. Margie Olympic, who lives in Newhalen, said "I was raised on a commercial fishing boat in Dillingham. Back in the day, we used to make enough money to support the entire family. Nowadays, fishing can only buy a few groceries or just catch up on bills"
Pebble Limited Partnership plans to build the Pebble mine near the village of Iliamna, which is the other Native Alaskan village that is close to the mine site. The villagers say that they are for the mine being built.
"Our villages are in decline. Commercial fishing has become too expensive."
The Native Alaskan's in charge of the Alaska Native {Nuna Resources} stated:
"Nuna Resources and its native village constituency want the Pebble Limited Partnership, to be given a fair hearing for its claims of environmental and cultural protection on Native traditional lands."
"Nuna's board of directors cannot compete with the large donors financing the campaign to "Stop Pebble Mine" and "Save Bristol Bay." Deep-pocketed individuals and companies like Tiffany Company Foundation."
Tiffany, Zales, and 58 other jewelry retailers have vowed to boycott Pebble gold by signing a "No Pebble Pledge." Anisa Costa, president of the Tiffany & Co. Foundation, offers this: "We strongly believe Bristol Bay to be one of the world's most pristine landscapes, home to a wild and productive salmon fishery which supports the ecosystem and the native communities around it. The proposed Pebble Mine would have a devastating long-term impact. . . . We are proud to sign the Bristol Bay Protection Pledge and urge other U.S. jewelers to do so."
"We are facing a dire economic situation. During the salmon fishing season, even in the best years, locals fish only during a three-to-four week season, then go back to villages where there are no jobs. Families are crushed by the cost of living there -- milk costs $9 a gallon and gasoline is $8 a gallon."
"The Pebble mine", Reimers said, "would create a local economy, with year-round work for thousands.
The Alaska Peninsula Corporation, which consolidated five tribes controlling 400,000 acres in the Kuichak watershed, which feeds the Bristol Bay area, have not taken a position for, or against the Pebble Project. In order to do so, they insist that due process be followed. "Only then can we consider its benefits and risks. If due process isn't followed, and the mine is blocked, "the lost opportunity
for jobs could cause irreversible disappearance of our culture."
Pebble opponents seem to be fine with that outcome.
On November 19th, Alaska Peninsula Corporation Signed a Land Access Agreement with Pebble Partnership.
{Greg Anelon} also lives in Newhalen, a dot of a village in Southwestern Alaska, next to Iliamna, its sister village. Both villages are about 15 miles from where the Pebble mine will be located.
Greg Anelon wants to raise his children in the area, but doesn't see a future for his village without the mine and the development that will result from it; namely, inexpensive electricity from the Pebble power plant, which will also help the other villages in the area. The low cost fuel that the mine will be bringing to the area, and the roads that Northern Dynasty will build, will also benefit the area.
Before Pebble arrived, the villages of Iliamna and Newhalen were in severe decline: no jobs, no money, escalating food and fuel costs. Few could afford the fuel and equipment needed to commercially fish the prized sockeye salmon in Bristol Bay.
Anelon agrees fish are more important than gold, but first it has to be shown that the Pebble mine will be a danger to the salmon. Plus the salmon are becoming less financially relevant to the people in the area. That is because, even for the residents that aren't directly involved in salmon fishing, they still can't benefit during the fishing season, by getting jobs processing the fish, because more than 86% of seafood processing jobs in Bristol Bay go to non-Alaskan residents. He notes that few residents in his area can make ends meet solely through commercial fishing.
" I see enough infrastructure in the area to keep our village alive. Another village in the area, Pedro Bay, lost its school last fall because of too few children attending. "I'll do anything to make sure the kids live in the village and stay in school."
Another Native Alaska group, the Arctic Slope Regional Corporation stated: "The nation's environmental laws are premised on the belief that science, rather than the kind of general information and speculation contained in the Bristol Bay Watershed Assessment (BBWA), should govern decisions."
More Native Alaskan's are for the mine than people realize
Some of the FAKE FACTS anti-Pebble groups are using
FOREMOST
HOW IMPORTANT ARE THE SALMON
TO NATIVE ALASKAN'S?
2018 was the highest sockeye salmon run in Bristol Bay since 1980. {Half} of the Bristol Bay residents are Native Alaskan's, but few were able to take part in the orgy of salmon fishing that was taking place.
In order to prevent over fishing of the salmon, in 1973, Alaska created a limited entry system that capped the number of permits of salmon fishing boats. The permit holders can hold on to the permits, or sell them.
Major foreign fishing conglomerates ended up with {64%} of the permits. Native Alaskan families, and Alaskan residents, held the other 36% of the permits, and this was enough permits to service the Alaskan residents and Native Alaskans that wanted to be involved in salmon fishing. However, the number of Native Alaskan families involved in salmon fishing has been steadily dropping, and by 2013 81% of the permits belonged to non-Alaskan holders. That trend is still continuing.
Once a family sells a permit, it is basically gone, because they are so expensive to buy back. It can {cost} up to $200,000 to buy a permit.
Alaskan youth are no longer committing to a salmon {fishing career} and so their family permits may end up being sold.
It used to be that an Alaskan Native, or resident, would get into their trawler and go salmon fishing when the salmon were running. They would spend all day fishing, before heading in to shore. They did not pack the salmon in ice because their trawlers did not have the capability to produce ice, and they did not buy the ice on shore, because the high cost of electricity made ice too expensive to buy, especially with the large amount of ice needed. And most did not have a refrigerated hold in which to put the salmon.
Very few people can afford to buy one of the new fishing vessels that are equipped with a refrigeration unit, because they cost $400,000.
Upgrading their present trawler with a refrigerated sea water system would cost $30,000 for the system itself. In addition to that, the trawler would require expensive hydraulic modifications, fish hold modifications, and other renovations. Again, too expensive for most people.
A salmon pulled out of water and left in the hold at 59 degrees F for 4 hours, will lose a day of shelf life (equivalent to how long they would be on a grocers shelf). It would lose even more shelf life if the temperature was above that. Because the ships are out in the large bay all day, the salmon could be in the hold for multiples of the four hours, which would mean that they could have lost many days of shelf life before the ship made it back to shore.
Even so, all the salmon would look fresh. Because of that, it used to be that Native Alaskan fishermen/fisherwomen, would get a decent price for their salmon. But now, a hand held device from from {Seafood Analytics,} can indicate how far the salmon have deteriorated. For years, buyers have been paying Native Alaskan fishermen less and less for their catch, because they were not putting the salmon on ice. Starting this year the buyers are {refusing} to buy salmon that have not been put on ice after being caught. Very few Native Alaskan's will be able to meet these requirements.
Most of the salmon {harvesting} takes place between Juneand and August.
During the rest of the year, Native Alaskan's, even the ones that still own fishing boats, need to find work, and there are few jobs available.
Activist's keep saying that Native Alaskan's have been fishing for salmon for thousands of years. That the salmon need to be protected in order that Native Alaskan's can retain their way of life, and financial livelihood that they earn by fishing the salmon.
That has been taken over by out of state commercial fishing fleets.
< Salmon fishing is no longer a way of life >
<<< for Native Alaskan's >>>
Critics say Pebble mine will only last 20 years,
The Pebble deposit has only been partially explored, but it is already
Pebble is a giant ore deposit. World wide, other mines of comparable size, stay in production for well over a hundred years, such as
Chuquicamata, which has been in production since 1910.
What are the arguments that critics are using against the Pebble mine
Opponents say the ore grade is so low that it would not be economically feasible to build a mine
Pebble contains a concentration of 0.61% equivalent copper (Eq Cu). Seabridge has the KSM mine whose copper concentration of 0.61% Eq Cu, is similar to Pebble, and Seabridge's mine is very profitable. There are even profitable mines with grades as {0.15%.}
Most major mines have cash costs of more than $1 per pound of copper. They are still very profitable mines, because the price of copper is over $2.50/pound. The Pebble mine would have cash costs of {$0.53} per pound of copper. A world class low copper cost mine.
Pebble would be one of the most profitable copper mines in the world
.................................................................................
People have also been led to believe that Pebble is next to Bristol Bay, but it is {100 air miles} and 230 river miles from Bristol Bay. They have been led to believe that any tailing's spillage will empty directly into the rivers and streams flowing into Bristol Bay. Supposing that there was spillage; unlike what the environmentalists state, the Pebble mine will only be near tributaries that account for less than {1%} of the Bristol Bay Drainage system.
The EPA, in its opposition to the Pebble mine, said that Pebble would devastate the area because it was near the headwaters of the ecologically sensitive Kvichak and Nuahagak watersheds.
But the Upper Talarik Creek is not the headwaters of the Kvichak River, and the Koktuli River is not the headwaters of the Nushagak River.
Opponents say
The Pebble area is earthquake prone
It is impossible for Pebble to be designed to withstand the strong earthquakes that occur in Alaska
This is the same argument that was made about the Trans Alaska Pipeline. What insights can be gained from that debate?
The Sierra Club asserted that the pipeline had basic design flaws which could not be overcome, even by engineering ingenuity, because the pipeline would cross the Denali fault, one of the most active and most powerful earthquake zones in the world.
A report from {top ecologists} at the Department of the Interior claimed that any one of 23 major earthquakes of the last 70 years would have caused a catastrophic break in the proposed pipeline.
According to the standards for building pipelines at that time, their conjecture was true. But they, and the Sierra Club, were wrong in thinking that ingenuity could not overcome the problems poised by earthquakes.
The oil companies were able {design} a pipeline capable of withstanding an 8.5 magnitude earthquake. The pipeline specification was for it to be 48 inches in diameter. Normally, that large a pipeline is easily ruptured, but they found a company in Japan that was making 48 inch pipelines with elastic properties so that it could bend under pressure, such as would occur during an earthquake, and return to its original form when the pressure subsided.
To test it under even more extreme circumstances, a section of the proposed pipeline was attached to huge frames, and massive loads were applied so that the pipeline wrinkled, and buckled, and finally folded in on itself, but it still did not rupture, and was even able to hold its pressure.
Over active fault areas, the pipeline was attached to sliders with Teflon shoes that were free to slide on long horizontal steel beams so that the pipeline could move 20 feet sideways if the ground moved sideways during an earthequake.
The pipeline was built with a series of curves so that it could stretch like an accordion if the ground move lengthwise.
The pipeline was flexible enough, and was attached to the beams in such a way, that it could move vertically, up or down, a distance of 5 feet.
Years later, after the pipeline was built, this was put to the test. On November 3, 2002, a 7.9 earthquake occurred on the Denali fault. It was the strongest earthquake ever recorded on the Denali fault.
To put that in perspective, that was 10 times stronger that the 1906 earthquake which destroyed San Francisco.
The ground under the pipeline moved 7 1/2 feet horizontally, and 2 1/2 feet vertically. The violent shaking damaged a few of the pipeline's supports near the fault, but that was it. It just required minor repairs.
The description of the measures taken to protect the pipeline against earthquakes might be hard to visualize, so here is a view of the pipeline at the Denali fault.
What does this have to do with the Pebble mine?
Environmentalists, and other anti-Pebble foes, including the {Sierra Club}, that was opposed to the Trans Alaska Pipeline, insist that not even engineering ingenuity will make it possible to build a mine that can withstand a strong earthquake.
As shown by the Trans Alaska Pipeline, this argument has no substance. There is no way to know what ingenuity can accomplish.
Critics say
It is not a matter of IF, but WHEN a catastrophic Pebble mine failure will occur because of the strong earthquake's in the area
Even though there is earthquake activity in Alaska, including the massive 1964, magnitude 9.2 earthquake, which occurred in the Prince William Sound region of Alaska, and which many environmentalists point to and say it would destroy the Pebble mine if it happened again, it, in fact, did not affect the Pebble site.
The closest earthquake fault to the Pebble site is the Lake Clark Fault. The U.S. Geological Survey (USGS) concluded that there have been {No Earthquakes} along the Lake Clark Fault in the last 1.8 million years.
Northern Dynasty's proposed mine would be able to withstand an earthquake stronger than any that have occurred in the area in the last {2,500 years,} as determined by the United States Geological Survey.
Some critics have said that the area's earthquake faults could extend under the Pebble mine site, and that if a 7.8 magnitude earthquake occurred directly under the Pebble mine, it would cause a catastrophic failure of the mine.
The reason no earthquake faults have been found under the Pebble site, is because, if any are there, they were too small to have been uncovered by the USGS mapping of the area.
The magnitude of an earthquake is related to the size of the fault.
The Pebble mine has been designed to withstand a 6.5 magnitude earthquake occurring directly under it. A 6.5 magnitude earthquake is an extremely powerful earthquake and it would not be possible for a small fault to produce an earthquake even close to that magnitude. Any earthquake that could happen, would be less than that.
Critics say that that is not possible to build a mine that could withstand a 7.8 magnitude earthquake, but already there are mines that have been built to withstand earthquakes even stronger than a 7.8 magnitude earthquake.
Chile is a seismically active region, and in 1960 experienced a magnitude 9.5 earthquake, the highest ever recorded by modern instruments. Because of its seismic-risk status, its mines, some of which are the largest in the world, are built to withstand the massive earthquakes of the region, and none have failed.
Neighboring Peru, which is also earthquake prone, has some of the world’s highest tailing dams for large-scale operating mines. Tailings facilities at the Cerro Verde and Antamina mines are reaching heights of 820 feet and 886 feet, respectively.
These modern tailings facilities in Peru are designed and built to withstand intense, high-magnitude earthquakes. The height of their embankments are much greater than any that are proposed for the Pebble Project.
Critics were besides themselves, screaming that the Pebble dams would be so high that they were bound to fail. Pebbles' original dam was going to be 740 feet tall. The newer, smaller version, will be 600 feet tall. Both are significantly shorter than the Peru mines. And just like the Peru mines, they will be able to withstand intense, high-magnitude
earthquakes. But of course, the critics knew this.
Critics point to the recent Mount Polley tailing dam disaster of 2014, because the designer, Knight- Piesold will build the Pebble mine
Therefore, critics say, Pebble's tailing dam will also fail.
Their argument doesn't hold water, pun intended.
During construction, the company {ran short of rock fill} in the area, the material used in the construction of the dam. In response to having less building material, and against Knight-Piesold's objections, they made the dam thinner.
The second problem was that the dam was built over a layer of glacial lacustrine soil (glacial silt), 25 feet under the ground. When subjected to increasing pressure, it changes from a solid, to a fluid. This is what happened when it was subjected to the increasing weight and pressure from the toxic waste and water that was accumulating behind the Mount Polley earthen dam.
Northern Dynasty is having an independent peer review group of scientists critique Knight-Piesold's engineering company's plans, and states that the regulators will follow the peer review groups' recommendations.
Northern Dynasty chose Knight-Piesold to construct the Pebble mine because of their extensive knowledge and expertise in building giant mines. The Pebble mine will be built to strict specifications as overseen by the government and scientific peer groups.
How are the valuable metals extracted, what ends up being discarded, why is it toxic
The most dangerous part of a mine is the toxic liquid wastes which are held in place behind a tailing dam. If a section of the dam breaks, the acidic water, and its accompanying toxic slurry, would pour out into the surrounding area, including any nearby streams and rivers, devastating the area.
What are tailings? They are what are left over after the minerals have been extracted from the ore:
To extract the copper, molybdenum, and gold etc. from the ore (rock that contains the metals) the rock is crushed into finely ground particles (150 micron size).
The crushed ore is transported to large froth flotation tanks filled with water mixed with chemical agents that form bubbles (froth) as well as chemicals that help separate metals from the rock substrate. This slurry of crushed ore and water, is conveyed along the length of the tank, where air is injected through the bottom of the tank. The injected air causes bubbles to rise up through the slurry, and then rise to the surface of the water.
One of the chemicals in the water, is the frother promoter,which strengthens
and stabilizes the bubble's surface so that it doesn't burst, but stays as a froth on top of the water. The water also contains bipolar chemicals, in which one side of the molecule attaches to a specific metal, such as copper, and the other side of the molecule attaches to the surface of the bubbles. The bubbles then transport the copper, etc. to the surface of the tank as froth.
As the slurry makes its way towards the terminal end of the tank, paddles skim off the froth as it forms. The froth is transported through a series of tanks, which contain depressant chemicals. Each tank contains a depressing compound which acts on a specific metal, such as copper, and depresses its ability to adhere to the froth, causing it to sink to the bottom of the tank. In this way the different metals are separated into their own tanks, and then can be further concentrated.
At the end of the process, the water, along with its residual chemicals, is recycled, while the slurry which has had the economical metals extracted, and is at the tail end of the flotation tank, is discharged into a collecting site, and forms, what's called a tailing pond, which is contained behind a dam, called a tailing dam.
This slurry contains pulverized pyrite, FeS, a left over, non-valuable ore. The sulfur in the numerous tiny particles of pulverized pyrite readily react with the oxygen in the air, and the water in the holding pond, to form a solution of sulfuric acid - battery acid.
The Pebble deposit also contains small amounts of arsenic and heavy metals, such as cadmium, all of which would be dissolved by the sulfuric acid and go into solution, making the tailings pond's contents {toxic} as well as acidic.
What about the accusation that there in no way to design a dam so that it can withstand a large earthquake
How would engineers know how to build a tailing dam to withstand an earthquake
There are {mathematical methods} that take into account the cohesiveness of the soil, how it would act during an earthquake, and how stable a dam would be depending on the slope of the dam's walls.
The stability factor (SF) can be calculated depending on the shearing strength parameters of the soil and the dam.
SF = tg / tgβ where, φ is the inside friction angle of the embankment and the material that composes it, corresponding to the shearing strength, and β is the gradient of the slope.
Other equations, such as those that take into account the balance of the vertical forces (∑ i X ) and of the horizontal forces (∑ i E ), would also be used in determining the design of the tailing dam.
There are other equations that engineers can use, and put together, it would allow engineers to design a tailing dam that would withstand an earthquake equal to the strongest possible earthquake that can occur at the Pebble site. The equations would also enable them to design the mine itself to withstand such an earthquake.
Taking into account, the density and viscosity of the slurry, and the forces that an earthquake of maximum determined magnitude will exert on the slurry, and the dam; engineer's will know the required shape that the dam should take so that it will retain its structural integrity.
This is a diagram of a tailing dam:
Engineers can calculate the required shape of a dam, but constructing it within parameters has been difficult, and if it isn't constructed to specification, it would be vulnerable to failure of the dam's wall.
Taking {ground based measurements} has proven to be imprecise because the ground will usually be too wet on which to drive a surveillance vehicle, and may even be too moist to walk on. There will only be scattered areas suitable for taking measurements, which will result in obtaining only a very loose estimate of the incline, as well as the thickness of the dam's wall. Ground based measurements have huge margins of error, so you don't know if the dam is being built within the engineer's specifications.
Even though radar or laser measurements are now being used and are more precise, they can only be taken where the ground will support the laser, or radar, and therefore the measurements will also only be able to be taken from scattered vantage points, which is imprecise.
{Drone-surveying} solves these problems. Drones can be automated, with flight planning apps taking care of the piloting and flying. Once it has finished surveying the dam, the data is uploaded into a processing platform, like Propeller, which views and measures the tailing dam in 3D. This will include highlighting areas of the dam where too much material has been deposited, causing a bulge; or not enough material, which would produce an indention in the mine wall. Both problems, a bulge in the dam's wall, or an indention, would cause stresses to form in those areas, and thus produce weak spots in those areas.
An even more efficient and accurate tailings dam wall monitoring procedure is coming into use, which would be perfect for monitoring the construction of Pebble's tailing dam.
Photo-satellite surveying, {PhotoSat,} takes high resolution stereo photographs (3D) accurate to within inches, of hundreds of square kilometers in minutes. This gives a view of the entire mine site, which will be delivered in record time to the mine's engineers, and it will be in a format suitable for immediate use so that there will be no delays on any corrections to the angle or thickness of the dam's walls. Thus preventing the development of any weak spots in the dam.
As these methods come into use, tailing dams will be able to be built to the specifications of engineers who can design a tailing dam to withstand any designated potential earthquake.
Critics charge that even if a safe dam can be built, that won't fail during an earthquake, the tailing pond, which is confined by the tailing dam, will leak acid tinged, heavy metal toxic water into the groundwater below it.
The groundwater, in its travels, would then contaminate the streams, rivers, and lakes in the surrounding area
There is now a way to prevent leakage from the tailing pond into the groundwater
The Kittila mine located north of Finland, inside the Polar Circle, is located in an environment, and yearly temperature range, similar to the Pebble mine. The Finland Ministry of Environment, mandated that it's tailing pond have a water tight liner.
For the floor of the tailing pond, the company used locally obtained glacial till. It was crushed and compacted into a 40 inch layer which ended up with a water permeability of less than 5x10E-8 m/s.
(BGM). The sheets of material are a composite, of which one component consists of the highest quality bitumen.
Bitumen is found world wide, but is best known as the tarry substance found in the La Brea Tar Pit in California. It is a sticky, black, and highly viscous liquid.
This is combined with butadiene styrene, a type of rubber with good abrasion resistance and good aging stability, it doesn't break down with age. The combination makes an elastic material that is also self sealing, the bituminous internal mass will flow and seal any punctures and penetrations.
These are combined with a sheet of glass fleece which is a dimensionally stable substance. Extremely high or low temperatures will not make it stretch or shrink. And even when physically stretched and stressed close to its point of rupture, it will return to its original size when the pressure is removed. It also has high strength with minimal weight. This makes the sheets of BGM light, but strong, and easier to maneuver and position so that they are correctly placed, and the glass fleece fabric prevents tearing of the composite sheet. It is also resistant to most acids.
Bituminous Geomembrane Liners stay flexible and do not stiffen, even at temperatures as low as -40°F. They lay flat, and in complete contact with the crushed glacial till floor of the tailing pond. Since they stay flexible, even at -40°F, they will mold themselves to any imperfections of the substrate over which they are being laid, even in deep sub zero temperatures, and will form a tight seal with the substrate. They also have a high friction coefficient and can be laid over even steeply angled dam walls.
The lowest temperature recorded at Pebble's site since 1947 is -31°F. Because temperatures at the Pebble site stay well above -40°F, even at the coldest times of the year, it would allow construction to be carried out year round at the Pebble site.
Based on the resulting composite's physical durability and resistance to punctures and tearing, and to most chemicals, the U.S. Navy Nuclear Safety Agency certifies BGM for a {1,000 year} life span.
BMG specifications call for it to be installed on a 2" compacted substrate, but in this case it was 40". The Pebble area has an abundance of glacial till available, so it could also lay down a thick compacted substrate, which in itself would be considered a water proof seal. The combination of BMG over compacted substrate is called a dual seal.
In addition to BGM being used on the floor of the tailing holding pond site, it would also be used on the inner wall of the tailing dam. This will ensure that there will be no leakage through the dam's wall.
In order to get to the ore in the deposit, an over burden of rock has to be removed. It is broken up, taken off site, and forms waste rock piles. These also contain iron pyrite, which is prevalent in the area. Because the pyrite is now open to air and rain water, it also generates sulfuric acid contaminated water, and Pebble critics say that it will seep down into the water table.
This is not a valid argument, because Northern Dynasty has stated that the waste rock will be stored in a lined, water proof, containment site. This would also be a dual seal. Critics also know this.
Critics say the tailing pond will have to be monitored indefinitely, and in the next hundreds of years, or even thousands of years, there is bound to be a leak, or spillage of the contents into the surrounding area, causing massive damage to the environment.
Therefore, no matter what, critics say that the Pebble mine is too dangerous to be built.
{Solidification,} which involves adding cement to the slurry, has a basic flaw.
Although the toxic metals are physically bound in the cement matrix, they are not destroyed. Cement is porous and their leaching into the environment would only be reduced, not stopped.
Other methods, such as adding chemicals to precipitate the heavy metals, would not only take huge amounts of chemical reagents, they also tend to produce secondary pollution.
Scientists are now studying the use of {bioremediation} to clean up, or neutralize toxic tailing ponds.
Bioremediation refers to the process of using microorganisms to remove toxic compounds, such as heavy metals and arsenic, from tailing ponds, as well as break down, and eliminate, the sulfuric acid that would be produced by Pebble's sulfide ores, but at this time, it is a very slow process.
The Pebble deposit contains iron sulfide, but because it is uneconomic, it is discarded into the tailing pond. The tailing pond also contains some of the economic metals because the present methods of extracting them, are unable to extract all of the valuable metals.
For instance, the Pebble tailing pond slurry will contain copper sulfide, because only {85%} of the copper will be extracted from the ore, which means that there will still be a lot of copper in the discarded slurry.
The crushed ore contains crushed sulfur, and the crushed sulfur will readily react with the water in the slurry, and the oxygen in the air, to form sulfuric acid, HSO.
In addition to iron sulfide and economic metals, the Pebble deposit contains arsenic and also dangerous heavy metals, such as cadmium. Because they are not extracted as the ore slurry makes its way through the froth flotation tanks, they will be in the spent slurry that is discarded into the tailing pond.
Arsenic can dissolve in plain water, but is most soluble in sulfuric acid tinged water with a pH of 2.65. It wouldn't have time to dissolve while going through the water froth flotation tanks, but it would dissolve in the sulfuric acid laced tailing pond.
The sulfuric acid in the tailing pond would also dissolve the heavy metals present in the pond's slurry, as well as the residual copper that was not extracted in the froth flotation tanks. The metals would go into solution as ions with a positive charge, such as Cd².
Cadmium, even in small amounts, is a deadly compound that can cause severe health issues, such as kidney failure. Arsenic causes neurological, lung, and heart damage. Copper is not very dangerous to humans, but even in trace amounts, it is deadly to salmon.
Bioremediation is cleaner and safer for the environment than chemical processing. The drawback of microbial leaching is the slow rate at which microbes work. Still, bioremediation is considered to be the only viable method of decontaminating large tailing ponds, but it needs {improvement} in efficiency. Bioremediation systems in operation today are slow and rely on microorganisms native to contaminated sites. Thus, today's bioremediation systems are {limited} by the capabilities of native microbes.
Humans, and most microbes, use oxygen (O), for respiration, which through a
A series of oxidation steps, using {electron transport,} produces ATP, a high-energy molecule that the cell uses for performing its various functions, such as reproduction.
If a microbe lives in an area where there is no oxygen, such as in a slurry, it uses anaerobic respiration, respiration without oxygen. The process uses a respiratory electron transport chain that does not use oxygen.
An example would be a microbe that uses {Sulfate (SO4),} or one that uses the electrons of metal ions, such as Chromium (VI) [Cr], for the electron transport of respiration.
Anaerobic respiration is not respiration like we know it. We breath air into our lungs, in order to obtain oxygen, which, through a series of steps is turned into ATP. During the process, carbon dioxide (CO) is produced, and expelled by the lungs.
Microbes don't breath gas, they absorb, or transport, the needed molecules, in their soluble ion form, through their cell wall, and through a series of cellular transactions, convert it into adenosine triphosphate (ATP).
Microbes also release their respiratory end product into the environment.
Sulfate-reducing bacteria neutralize sulfuric acid, because when they 'breathe' the sulfate (SO) part of the sulfuric acid, HSO, it is changed into sulfide (S²), which is then released into its surroundings. In eliminating the sulfate part of any sulfuric acid, that the microbes use for their respiration, they also end up, in effect, destroying and removing that sulfuric acid from the slurry.
In addition to that, the sulfide that is produced, (S²) and released into the slurry, will react with several of the toxic heavy metals in the slurry, such as cadmium (Cd²), which will form insoluble cadmium sulfide, CdS. Because the sulfide forms such a strong bond with the cadmium, the bipolar water molecules can't pull it apart into its separate ion components, Cd² and S², and it precipitates out of solution.
Since the cadmium is no longer in solution in the slurry's water, if there was a tailing dam break, and the slurry spilled outside of the dam, the cadmium would stay put wherever it landed. It would no longer be considered a contaminate to the surrounding country side.
The same thing would be true for the other toxic metals in the Pebble tailing pond, that sulfide could precipitate out of solution.
Antimony (Sb), Arsenic (As), Cadmium (Cd), Chromium (Cr), Copper (Cu), Lead (Pb), Mercury (Hg), Selenium (Se), Uranium (Ur), Zinc (Zn)
Precipitated as sulfides:
Antimony, Arsenic, Cadmium, Copper, Lead, Selenium, Zinc
Leaves:
Chromium, Mercury, Uranium
Getting back to neutralizing the sulfuric acid in the tailing pond slurry, as well as the toxic heavy metals. The best bioremediation method is to use a
Specific groups of sulfate-reducing bacteria are localized at different {depths} of the slurry in the tailing pond.
The part of the slurry near the surface contains some oxygen, but turns more anoxic as the depth increases. This alone would cause the microbe composition to change according to the depth of the slurry, because some microbes function better if some oxygen is present, and others function better with out any oxygen.
Different microbes would be dominate at different depths.
The types of ore, in the Pebble deposit, varies through out it, and as it is processed, and then discarded into the tailing pond, it will cause the tailing pond to have different combinations of metal in different parts of it. This will change the composition of the microbes in those areas. The varying metals will attract bacteria that use those specific metals for their respiration.
When microbes are first introduced into a contaminated site, they are {not very effective} in removing the contaminants. But, over time, each of the differing areas in the tailing pond will become populated with microbes best suited to that area. As they multiply in numbers, they will remove greater and greater amounts of sulfate and heavy metals at the sites, and the rate of remediation will increase.
By introducing a combination of microbes into the tailing pond, instead of only a few types, it will make it more likely that there will be microbes available that will be best suited for the different environments in the tailing pond.
Eventually, the rate of detoxifying the pond will increase more than having the most efficient microbes present at the differing sites can account for. This is because microbes have plasmids's.
A microbe's cytoplasm, in addition to having a large chromosome which directs the microbes functions, has multiple tiny circles of DNA, called plasmid's, floating in its cytoplasm, which work at protecting the microbe from outside dangers. These are how bacteria develop antibiotic resistance. It is also how microbes develop the ability to survive in toxic environments.
If a single bacteria developed resistance to an antibiotic, it wouldn't do much good for the other bacteria in the colony. The colony's of bacteria that could incorporate the protection developed by a bacteria in their colony, would thrive, compared to colony's that didn't have this ability. Over time, bacterial colonies that were able to transmit favorable genes to each other thrived, as their colonies were able to outperform competing colonies.
Now all bacteria have the ability to pass on beneficial traits to other bacteria.
Even different strains of bacteria can transmit beneficial traits to each other. For example, resistance to cadmium and cobalt was transferred to the {completely different strains} of bacteria, E. coli to A. eutrophus. Some microbes are more efficient than others in removing heavy metals, and as these genes are transferred to other microbes in a slurry, the cleanup of the tailing pond increases in efficiency.
Different microbes use different methods of removing toxic metals. Some microbes {chelate} the metals. Chelate is Greek for claw. The microbe binds the metal in two places and forms an irreversible bond, which in effect, removes the metal from the slurry.
Other microbes produce {calcite} and bind metals such as lead and cadmium inside it, which isolates the metals from the slurry.
Others use metals as part of their {respiration,} such as using soluble chromium (VI) Cr, and in the process of respiration, changing it into insoluble Cr³, which precipitates out of solution.
Some microbes form a {coating} around themselves which contains pockets with negative cations which bind to the positively charged metal ions, and binds them in the coating. The coating, with its embedded metals, periodically sloughs off of the microbe, which leaves the metals embedded in the slurry, and no longer in solution.
In a test site, researchers added five different types of microbes, that used different means of neutralizing toxic metals. The efficiency of the microbial removal of toxic metals increased by a factor of 14.
Science has barely started to discover the microbes that can make heavy metals less toxic. Currently {less than 1%} of the microbes that can detoxify heavy metals, and arsenic, are known to science.
Over time, more will be discovered, and this will increase our ability to make tailing pond's safe.
Scientists are learning how to take genes from bacteria that use different methods of detoxifying heavy metals, and transcript them into plasmids, which they then insert into bacteria, and greatly enhance their ability to remove toxic metals from contaminated sites.
They were able to genetically engineer a microbe that was able remove {25 times} more cadmium and mercury than the microbes native to the site.
What about the toxic metals, Chromium, Mercury, and Uranium, that are not precipitated by sulfate reducing microbes?
{Uranium} is found throughout Alaska, although usually not in a large enough quantity to mine.
Sulfuric acid turns uranium into the very soluble U, which, even if it is not present in large amounts; since it is in solution, if there was a tailing dam breach, it could be carried long distances and present a danger to the area.
Microorganisms have been found in uranium tailing's that use soluble uranium (U) as an electron acceptor for their respiration, and end up changing it into insoluble U. These microorganisms could be used in the Pebble tailing pond, to precipitate any U that was present in the slurry.
Soluble chromium VI (Cr) is one of the most toxic heavy metals known. Insoluble {chromium III} (Cr³) has only one thousandth of the toxicity of Cr.
A {wide range } of microorganisms that use soluble Cr for respiration, and change it into insoluble Cr³, have been found in contaminated sites. So there is no shortage of microbes that can be used at the Pebble site.
In addition to that, heavy metal levels do not have to be brought down to Zero. The EPA has designated safe levels for each metal, and arsenic. The levels of the various contaminants will only have to be brought down to the levels listed as safe by the EPA. Future bioremediation will effectively accomplish that goal.
Mercury is in a deadly category by itself. Microbes get rid of any mercury that enters them by changing it to organic {methylmercury} which they are able to transport through their cell wall and into the surrounding environment.
If methylmercury enters a river, lake, or the ocean, which could happen if it escaped from a tailing pond, it would quickly be taken up by the aquatic wildlife, because methylmercury is readily absorbed in the intestine.
Because it is hard to break down methylmercury when it has been ingested,
it works its way up the aquatic food chain, and is eventually consumed by humans. It is severely neurotoxic, especially to a pregnant woman's developing fetus. So it is a strongly banned substance, and authorities would not want there to be a chance of it getting into the ecosystem surrounding the Pebble tailing pond. If there was a way to eliminate it, there would be a greater chance that the Pebble mine would be approved.
Previously there was no reliable way to remove it from giant tailing ponds. However, a group of methylmercury dismantling bacteria have been found that take up methyolmercury, and {break it down} into harmless components. They would prevent the build up of any methylmercury that might be produced by microbes in the Pebble tailing pond.
Complementing that, a bacteria has been genetically engineered that contains mercury scavenging sites. The sites isolate and contain the mercury, which prevents it from harming the bacteria. These bacteria can survive an environment containing {24 times} the dose of mercury that would kill non-resistant bacteria. They remove the mercury from the area around them. In a test of such an environment, in just 5 days, they removed over 80% of the mercury present in the solution.
Adding them to the Pebble tailing pond, would bring down any methylmercury present in the slurry to such low levels, that very little would be produced. The methylmercury dismantling bacteria would then easily remove any methylmercury that might enter the slurry.
By the time Pebble is ready to build its mine, bioremediation will have advanced to the point where tailing ponds will no longer be considered a threat to the area
What are the chances that the Pebble mine will receive approval
Similar to Pebble, the Donlin Gold project is located in southwest Alaska, and is seeking approval to build a mine. It's 39 million ounce gold deposit has a high mercury content.
Environmental groups have been opposing it, and so have several Alaskan tribes. This April the U.S. Army Corps of Engineers issued its Environmental Impact Statement (EIS) {approval.} They concluded that the company's mine design would prevent the mercury from escaping the site. They also approved the 315 mile long natural gas pipeline that the company wanted to build.
The company will now have to get 100 permits approved before they can begin construction of a mine. The state and federal agencies that issue the permits, will use the EIS to {guide} their decisions.
The company received an EIS approval, even with their deposit having a high mercury content, and their planned mine is near the Kuskokwim River. The U. S. Army Corps of Engineers concluded that the the company's construction plans were so well thought out that they would protect the countryside from even the most severe adverse effect that could threaten the mine site.
Pebble has a thoroughly thought out and documented mine plan, and so it should also receive an EIS approval, although this is not a certainty.
Will the Pebble mine make a significant difference in the amount of America's holdings of strategic metals
The geology of how Pebble was formed shows how much ore could be in the Pebble deposit and surrounding area.
The Pebble deposit formed 90 million years ago. At that time the tectonic {Pacific Plate} that formed the ocean floor next to Alaska, was colliding with, and sliding under, the Alaskan continental plate. When it descend to a depth of {35 miles} the oceanic rocks started to melt. The heavier sections continued on downward, but the lighter, buoyant, melted sections, took on the aspects of a lava lamp, and all along the arc of the colliding plates, hot elastic sections of the oceanic plate began an ascent towards the underside of the continental plate. (This hot, melted rock is called magma. If it makes its way to the surface and erupts from a volcano, it's called lava.)
Melted oceanic rock contains small amounts of various metals spread throughout it, but in very low concentrations, such as 30 parts per million for {copper} and a few parts per billion for gold and silver. The total amount is large, but it is too diffuse to be economic.
Oceanic rock contains sulfur, which turns to hot liquid sulfur, when the rocks that form the floor of the ocean melt and turn into magma, as they descend to the 35 mile depth. Liquid sulfur droplets, circulating throughout the magma, scavenge transition metals, such as copper, gold and molybdenum, and concentrated them up to
{100,000} times their normal levels.
As the plume of melted oceanic rock continued upward, it passed through a
{layer} of metal enhanced molten rock, which further {enriched} the oceanic magma plume, with metals such as copper and gold. And this additional metal was also incorporated into the liquid sulfur.
The rocks that form the ocean floor have numerous open spaces, called pores, between the particles that made up the rock. Many of these open spaces are filled with salty ocean water (brine). At the depth where the oceanic plate melts, the pressure squeezes the atoms of the brine molecules so tightly, that, even though the magma is red hot, the brine can't turn into steam.
In the high temperature and pressure of the magma, the intensely hot brine becomes very reactive and the chlorine in it (NaCl) scavenges metals and concentrates them
Even normally inactive gold, forms soluble compounds in the circulating hot brine, such as {hydrogen gold chloride} (HAuCl2).
Mineralized porphyry deposits form over {durations} of a few hundred thousand years, to periods of several million years. {Giant} porphyry copper deposits require sufficiently long periods to accumulate large ore deposits. In addition to duration, magma that contains large amounts of copper, and associated metals, such as the magma associated with the Pebble deposit, will significantly increase the amount of ore that is formed.
The magma producing events that formed the Pebble ore deposit extended over a time scale of {3 to 4 million years,} which is {longer} than the duration of most porphyry producing episodes. Fresh, metal rich plumes of magma, repeatedly rose from a deep magma chamber, mixing in with the magma that was forming the Pebble deposit, and preventing it from cooling and solidifying, as well as replenishing it with additional quantities of metals. For millions of years, additional metal was repeatedly added to the Pebble deposit, eventually making it the largest ore deposit that has ever been discovered.
The hot molten magma that formed the Pebble deposit worked its way upward, cooling slightly as it rose, and becoming less molten, and thus thicker, until it could not work its way any higher, and ended up at a depth of {3.8 kilometers} (2.4 miles).
The metal enriched hot brine from the magma, then rose upward through cracks in the overhead rock. The hot brine, which is called hydrothermal fluid (hot water), can carry extraordinarily high concentrations of metals, such as {10% by weight} copper.
{Hot brine's} hold in solution greater concentrations of metal than cold brine's. As the brine from the magma moved toward the surface, it cooled, and by the time it reached Pebble's location, it cooled to the point where the metals started to precipitate into the open cracks and pores in the rock.
In addition to the water already present in the magma, surface water seeping through cracks in the rock, worked its way down to the magma chamber. Over the distances traveled, water picks up impurities, including salt.
As this salty (chloride containing) water entered, and circulated through the hot magma, it in turn, absorbed metals, plus the metal enriched sulfur, that had not been captured by the original brine that was in the magma.
This, now metal enriched water, that was circulating in the hot magma, in turn rose towards the surface, and added more metal to the evolving Pebble deposit. This continued for millions of years as fresh plumes of hot metal containing magma worked their way up into the magma chamber that was feeding the Pebble site.
How much ore are we talking about?
Pebble has been {drilled} to a depth of a little over a mile, 5,900 feet, which is 1.1 miles, and the drills were still encountering ore in quantity. In fact the grade of {molybdenum} was increasing with depth.
Molybdenum and copper and gold start precipitating out of hydrothermal solutions at a depth of {2.3 miles.} The magma chamber that produced the Pebble deposit is located below that, at a depth of 2.4 miles. This is far enough down, that the metals in the Pebble deposit, could have been deposited starting at a depth of 2.3 miles.
The Pebble deposit has been drilled to a depth of 1.1 miles. Mo, Cu, and Au most likely started precipitating out into the Pebble deposit at a depth of 2.3 miles. This means that Pebble's ore deposit could be more than double its present depth.
The Pebble deposit is open outward to the E, S, NW and SE. In those directions, the drills were still encountering full strength ore. This indicates that, in addition to the Pebble deposit being much deeper than presently delineated, it could be much wider. Therefore, the amount of ore in the Pebble deposit could be much greater than is presently listed.
Pebble's molybdenum ore, molybdenite, contains high concentrations of the critical metal, rhenium, whose high melting point of 5,725° F and, stable crystalline structure, that resists {creep_deformation,} makes it ideal for rocket and stealth {jet engine} turbine blades.
Molybdenum itself is a critical metal. When molybdenum is added to steel, it forms an ultra-high-strength steel that will maintain structural stability when placed under pressures reaching as high as 300,000 lbs/sq. inch.
Molybdenite (molybdenum + rhenium) increases with {depth,} and therefore the deeper the Pebble ore deposit is extended, the greater the proportion of molybdenum and rhenium it could contain.
And this could be just a tiny amount of what is actually there to be found
magma that is located 6 miles underground. Ninety million years ago, this batholithic magma chamber was molten, and, in addition to forming the Pebble deposit, this giant 350 square mile magma chamber sent up multiple plumes of magma throughout the area. These could have produced additional ore deposits, which may be similar to the Pebble deposit, because they were produced from the same magma chamber that formed the Pebble deposit.
The United States Geological Survey states that the mineralized area around Pebble is the most {extensive} in the world and could host multiple deposits in the area.
Pebble is in an area that is poorly explored because of an extensive cover of glacial debris. A regional-scale airborne {aeromagnetic} survey was conducted to penetrate this cover and see what was under it.
Analysis of regional aeromagnetic data showed a 250 mile long magmatic arc in southwestern Alaska, extending to both the northeast and southwest of Pebble, that was similar in age to the Pebble deposit that was formed 90 million years ago. The people doing the aeromagnetic survey concluded that the Pebble district is "highly prospective for porphyry-style deposits similar to the giant Pebble porphyry Cu-Au-Mo deposit."
The journal {'Economic Geology'} reported on aeromagnetic survey's done in the area and stated that examination of southwestern Alaska has disclosed a number of large deep-seated anomalies in a setting similar to the porphyry environment of northern Chile and that this "suggests that southwestern Alaska is highly prospective for porphyry exploration."
A {U.S. Geological Survey} reports clustered groups of anomalies 15-25 miles long by 12-18 miles wide along the Alaska Lake Clark fault and that they are the same age as the near by Pebble deposit. The spacing of the clusters are similar to the giant porphyry copper-gold-molybdenum deposits of northern Chile, and favorably suggests similar discoveries in southwestern Alaska.
In Chile's Atacama desert there are multiple giant copper-gold-molybdenum-silver mines. These mines are located along a {375 mile} long belt. Like the Pebble deposit, they are also giant deposits, because they formed over a 3 million year period of magmatic hydrothermal episodic pulses, which in their case, started 38 million years ago.
Chile's mines have been in production for over 100 years, such as Chuquicamata, which has been in production since 1910, and is still one of the largest ore deposits in the world. A hundred years of continuous mining has barely touched it. And, like
Escondida, another giant mine in the ore bearing belt, these mines are not composed of a single deposit, but a group of deposits located in the same general area.
Depiction of the multiple ore deposits (mines) in Chile's ore bearing belt.
There are ways to determine if more deposits are in
the area surrounding the Pebble deposit
An aeromagnetic survey is done by a plane flying over an area while transmitting a current which varies in strength. According to Faraday's law of induction, this time varying field induces currents in conductive features, such as ore, in the ground. These currents produce an associated (secondary) magnetic field in the ore that can be detected by an electromagnetic receiver on the plane. There is no need for the transmitter or the receiver to touch the ground, so electromagnetic systems can be mounted on aircraft and be used to explore large areas quickly and efficiently.
What that means, is, if there is metal ore in the ground, the plane will induce currents and a magnetic field in the ore, which will be detected. Once the plane passes past the ore bearing structure, the signal will stop, and thus the width, as well as the location, of the deposit can be determined.
The electronic signal is traced on paper, and the site it maps is called an anomaly (if the scan indicates that an area is different from the normal rock background, it is an anomaly.)
However, the scans can't tell you if they are detecting gold or fools gold. Fools gold, also known as pyrite, is iron disulfide, and the iron would give a strong signal. So, even though scans can detect buried ore deposits, they can't tell you if the ore is of any value. But scans do two things. They show where an ore deposit is located, after which the site can be tested to determine what ore it contains. Plus the scan also gives a signature of the ore deposit.
Since Pebble has been drilled, its ore content is known. The scans of any anomalies in the area around Pebble, can be compared to Pebble's scan and any anomalies who's signatures are similar to Pebble's, could be a similar type of deposit.
But drilling is very expensive, and so, even if you find an anomaly with a signature similar to the Pebble site, you want to be sure, if possible, that you are drilling a site with valuable ore. You would also want to know what type of ore it contains. If it is just iron, you would skip it. If it contains valuable metals, such as gold &/or copper, then you would want to drill it.
It turns out that there is a way to know what type of ore a site contains. Because most sites in the area that would be discovered by an aeromagnetic survey, have a thick overburden of glacial till, you could not directly take samples to see if the site contained valuable ore.
But, over time, atoms, and isotopes, of any buried ore, migrate to the surface, being carried upward by ascending water, etc, and can be detected in parts per billion, or even parts per trillion, on the ground surface over the ore site. Testing the surface over an anomaly can detect ore buried as deep as 1,800 feet.
There were two companies that had claims adjacent to Northern Dynasty, and
after they did airborne scans over their property, they performed surface geochemical studies over the anomalies that they located. The geochemical tests of the anomalies would show if the site's contained valuable ore.
Northern Dynasty later bought their properties.
The results of those studies have not been reported by Northern Dynasty
So I researched the subject myself
Liberty Star Uranium & Metals (LBSR), had property in the same vicinity, one side of which, was adjacent to Northern Dynasty's Pebble property.
The company, Full Metals, also had property, with one side of it adjacent to a section of the Pebble property.
Liberty Star Uranium and Metals Corporation spent seven years, 2003-2010, doing an extensive work up of their property, including airborne scans and geochemical testing of the anomolies that the scans discovered.
McPhar Geophysics did an aeromagnetic survey over LBSR's property. Geotech Ltd. conducted a 6,000 foot deep ZTEM scan over LBSR's property. The scans showed several sites that had large, deep, anomalous areas.
To determine what types of metals were present in the deposits outlined by the scans under the layer of glacial till, LBSR took 11,000 geochemical soil samples, 4,274 vegetation samples, and 993 water samples.
How does testing the { ground surface} of an anomaly, tell if it can contain any valuable ore
Especially if the ore is buried a thousand feet underground
Even though an ore deposit may be deeply buried, it can be detected by sampling the surface area of the ground above the deposit, because minerals and isotopes that are unique to the ore in the deposit will make their way to the surface, although only in tiny amounts. It used to be difficult to detect them, but new {instruments} that can detect compounds in parts per billion, and even parts per {trillion,} can now, not only detect them, but give an accurate measurement of their concentration. One ppt could be represented by detecting one yellow marble on 20,000 football fields (almost 39 square miles) covered with orange marbles.
Being able to accurately measure the metals is important because, if the instruments detect that the area has valuable metals, they can show up in the area away from a deposit, but in smaller amounts than what is present directly over the deposit. By being able to accurately tell the differences in the amounts of metal in the area, even if it is only a few parts per trillion difference, you can gauge where the center of the deposit is located, and the edges of the deposit. Using these instruments, it is now possible to detect ore deposits that are as deep as {1,800 feet.}
Testing ground samples
One method that is now being used, is testing for {resistate} porphyry indicator minerals, because they are more abundant than the valuable metals that are being sought, and so are easier to find, and at the same time, their presence indicates that the sought after valuable metals are also present. These are minerals that are resistant to erosion and destruction. The reason that they can indicate if there are valuable metals in the area with them, is because they are altered in hydrothermal environments that specifically produce the valuable metals. Even if they are deep underground, they make their way to the surface in trace amounts, and because they are resistant to destruction, weathering of the site won't destroy them. Their discovery will point to metal deposits hidden under the glacial till.
The word {isotope,} meaning at the same place, comes from the fact that isotopes are in the same place on the periodic table. Chemical elements, such as copper, can have different numbers of neutrons in their nucleus, but all its isotopes will have the same number of protons and electrons, and they will just be considered to be copper, with a different atomic weight. In addition to having a different atomic weight from the primary metal associated with them, they will have different chemical and physical properties. The isotopes will not only tell you which metals are present at the site, in certain cases, they will also indicate their depth.
Because of their differing atomic weight, isotopes have different {oxidation-reduction} reactions than the primary metal itself. Specific microbial communities that live underground use these isotopes for their metabolism. Some of these microbes, along with associated isotopes, are brought to the surface with ascending water. The metal isotopes will indicate what metals are present in the ore deposit, plus, since different microbes live at specific depths, the ones that were using the ore in the deposit, will reflect the deposit's depth.
Trees with deep tap roots, such as the Alder trees that grow in the area, absorb geochemicals, such as gold ions, from a large volume of soil and groundwater.
{Experiments} have shown that it is possible to locate buried deposits by comparing the amount of gold over an anomaly, to the amount of gold away from the anomaly.
Gold is a toxic metal to Alder trees, and is transported to its extremities, its branches, bark, and leaves. One of the tests LBSR performed was taking samples of leaves from the Alder trees over an anomaly, as well as from Alder trees away from the anomaly. The samples from the Alder trees growing over the anomaly's had 20 times more gold than trees growing 650 feet away from the anomaly, indicating a buried deposit on the site.
Water samples
Copper {isotope ratios} in ponds and streams can provide insight into buried metal deposits. Surface waters proximal to the deposit, and which likely interacted with underlying concealed mineralization, have heavy δ65Cu values which contrast with lighter values in waters distal from the deposit. .
Ground water going through a deposit picks up trace amounts of the metal contained in the deposit. These can be detected in nearby streams, or ponds, that incorporate the ground water. Comparing the amounts against known background concentrations, will point out locations that have higher than normal amounts of metal, as well as what type of metal, such as gold, that may be located beneath a nearby downstream site.
In 2004/2005, Northern Dynasty allowed LBSR to conduct geochemical and geobiological sampling on the soil over their Pebble deposit
That way LBSR could compare the results with the anomalies that they were evaluating, and see if any of them were similar to Pebble's surface trace mineral signature. In return, LBSR shared their results with Northern Dynasty.
***
Tests of the soil over the area of what would become the {Pebble East Zone,} showed that there was a deposit containing gold, copper, and molybdenum under that area, EVEN THOUGH IT WAS UNDISCOVERED AT THAT TIME, and under 1,000 feet of glacial debris. ***
Northern Dynasty's planned step out drilling encountered the Pebble East zone exactly over LBSR's geochemical signature of the deposit, and the drilling showed that the metals it contained, were the same ones discovered in the geochemical surface testing.
This shows that the geochemical/geobiological surface testing of a site
WILL BE ABLE TO TELL YOU WHAT METALS, IF ANY, IT CONTAINS
In 2007 - 2010, a {geochemical evaluation} of the Pebble property was done by the U.S. Geological Department of the Interior. In addition to gold and rhenium etc., the samples detected arsenic and mercury, as well as trace amounts of uranium. .................
LBSR's airborne scans outlined 7 large {anomalies,} that were 1.5 miles in diameter, plus 5 smaller anomalies.
Full Metals
Did an airborne survey that located 4 anomalies equal in size to the Pebble East and West deposits, (= to 2 Pebble deposits), plus 1 smaller anomaly. Geochemical sampling showed that all of them contained copper, gold, and molybdenum.
In July of 2010, Northern Dynasty formed a {joint venture} with LBSR, and LBSR's stock price went from $0.02 to $0.175
Having multiple deposits in nearby locations is not unusual. Escondida's giant copper-gold deposit in Chile, is actually a group of related deposits. Seabridge Gold's giant KSM copper-gold mine is also not just one deposit, but a group of deposits, all located in the same general area.
Northern Dynasty has indicated that if any deposits similar to Pebble are found in the area, they will be included in the Pebble project.
How big could the Pebble project be
The Pebble deposit is most likely double its presently defined size, so that is the same as adding another Pebble deposit. Adding that to LBSR's plus Full metal's properties would give 10deposits similar to the Pebble deposit in size, plus 6 smaller anomalies. Geochemical samples show that they all contain copper, gold, and molybdenum ore.
These figures only include the nearby LBSR and FULL METALS sites. Aeromagnetic surveys showed a 250 mile arc underlain by magma similar to which produced the Pebble deposit, and containing multiple anomalies. These could also be deposits similar to the Pebble deposit.
The AMOUNT OF ORE IN THE AREA, which Northern Dynasty can exploit, is BEYOND COMPREHENSION
What are the chances that it contains multiple deposits
{Donlin Gold's} original ore estimate was 29.1 million ounces of gold. In its financial statement CEO Greg Lang stated, "High grades of ore were found, not only in the original mine area, but in regions well beyond the current site. We believe that there's a lot more gold to be discovered at Donlin Gold."
Just like Donlin Goild, there are most likely multiple ore deposits in the Pebble area.
Pebble would also be important to Alaska
Pebble would supply generations of Alaskan families a secure financial future.
JUST AS IMPORTANTLY
PEBBLE WOULD SUPPLY AMERICA WITH CENTURY'S WORTH OF STRATEGIC METALS
All in all, Pebble's approval would benefit America, as well as Alaska